ES2785153T3 - Procedure and apparatus for the manufacture of a mechatronic system by three-dimensional printing - Google Patents

Abstract

Manufacturing method of a mechatronic system comprising: - a manufacturing step of a mechanical structure (SM) by three-dimensional printing by depositing molten wire of at least one first electrically insulating material (M1) (M1); and - a manufacturing step of at least one electrical component (CE) in contact with at least one element of said mechanical structure and integral with it; said manufacturing step of at least one electrical component is implemented by three-dimensional printing by depositing molten wire of at least one second material (M2), conductive or resistive, directly in contact with said element of the mechanical structure, characterized in that said or a said electrical component is a transducer (JC1, JC2), the method also including a local annealing stage implemented during or after depositing a layer of the first or second material, corresponding to said deposit.

Description

DESCRIPTION

Procedure and apparatus for the manufacture of a mechatronic system by three-dimensional printing

The invention relates to a method of manufacturing a mechatronic system, as well as to a manufacturing apparatus adapted to implement such a method. The invention is based on three-dimensional (3D) printing techniques, also called additive manufacturing. It lends itself to many applications, such as, for example, the manufacture of:

- portable physiological or activity sensors (heart rate, blood glucose ...);

- rehabilitation devices;

- two- or three-dimensional interaction interfaces;

- connected objects;

- etc.

Today, additive manufacturing techniques (or 3D printing) are experiencing an important boom in different fields and are preparing to revolutionize the industrial sector, but also the mode of consumption of individuals. In recent years, different procedures have been developed in order to design a great variety of objects and mechanical structures. They allow you to control local or global mechanical properties or also the appearance of objects (eg color or texture). However, these procedures do not produce more than passive objects, without the ability to perceive or act on the environment.

To make these active objects, electronic components and functions must be integrated there, which, at present, are manufactured separately, by substantially subtractive methods, then, they are assembled with a mechanical structure in industrial chains for the realization of a final object. Integrating electronic functions within a non-planar, non-assembly mechanical structure is challenging.

In recent years, a number of actors have been interested in the use of polymer materials for the realization of so-called malleable or organic electronics. This branch of electronics is relatively recent, since the first conductive polymers were made in 1977 and the first electronic components using these materials emerged in the mid-1980s. Today, organic electronics make it possible to make a number of electronic components, such as field effect transistors (OFET), photovoltaic cells (OPV), organic light-emitting diodes (OLED), electrochemical biosensors, even electroactive polymer-based actuators (EAPS). To carry out this electronics, new procedures have been developed and, at this moment, certain of them are used on an industrial scale, such as continuous or rotary web printing (flexography, gravure, ...). Ink jet printing (IJP) and aerosol jet printing (AJP), which are part of 3D printing procedures, make it possible to make certain organic electronic components, specifically, sensors [Muth, 2014; Sitthi-Amorn, 2015] and are currently the subject of intensive research on this topic.

However, these procedures do not produce more than a few components on planar substrates [Rossiter, 2009] or that require additional assembly operations, which, therefore, do not allow the design of complete mechatronic 3D structures. Recently, it has been proposed to use conductive polymers with the fused filament deposition 3D printing process (f Dm, from English "Fused Deposition Modeling") to print pressure sensors on 3D objects [Leigh, 2012]. Likewise, it has been proposed to use functional thermoplastics for printing elemental components, such as antennas [O'Brien, 2015].

The potential of polymer matrix composites has already been demonstrated for a number of applications, such as sensors and actuators: [Coiai, 2015], [Deng, 2014]. Furthermore, the science of nanocomposites and nanoparticles (cationic nanoclays, anionic nanoclays, noble metal nanoparticles, carbon nanotubes, etc.) has allowed a better understanding and better control of the synthesis procedures of these materials. In particular, thermoplastics that incorporate carbon fillers are promising for the manufacture of sensors, for example, strain, force, temperature, electrochemical (liquid or gas detection), etc. Compounds with a metal core (for example, copper) and a thermoplastic matrix, developed and integrated in an FDM printer, allow making strain gauges, are also known (see US 2014/328964).

At present, however, complete mechatronic systems cannot be 3D printed. Today, hybrid procedures allow this, but with limited potentialities. The most successful of these is the Voxel8 platform (www.voxel8.co), derived from Harvard University, which combines the FDM for the object structure, a metallic ink for the conductive tracks of the circuit and a positioning system. of discrete components.

A method for manufacturing a mechatronic system comprising an electrical component is known from document US 2015 / 173,203. However, this electrical component is not a transducer. Document US 2015 / 173,203 also discloses an apparatus for the implementation of said procedure that comprises three integral print heads.

It is also known from document WO 2014 / 209,994 an apparatus for the implementation of a process with a molten yarn deposit comprising several recording heads that can be controlled independently. Furthermore, document US 2010/0021580 A1 discloses an additive manufacturing apparatus according to the preamble of claim 7.

The invention aims to overcome the aforementioned drawbacks and limitations of the prior art. More particularly, its objective is to allow the manufacture, in a single piece and by the same 3D printing process, of the mechanical subsystem and of at least a part of the electrical subsystem of a mechatronic system. The term "electrical" must be interpreted in the broad sense, consisting of functionalities of an electronic and / or electromagnetic type, including optoelectronic.

In accordance with the invention, this purpose is achieved by using the three-dimensional printing technique by depositing molten wire to manufacture both a mechanical structure and at least one electrical component (conductive track, resistance, sensor ...) integral with said structure. , for example, arranged on its surface. This necessitates the use of at least two different materials: a first material, electrically insulating, used to print the structure and at least a second material, conductive or resistive, used to print the electrical component (s). In this way, the inconveniences of hybrid techniques are avoided: extra cost due to assembly stages, mechanical fragility, necessary space ...

Therefore, an object of the invention is a method of manufacturing a mechatronic system according to claim 1.

Also another object of the invention is an apparatus for implementing a method, as mentioned above, in accordance with claim 7.

Other characteristics, details and advantages of the invention will become apparent upon reading the description made with reference to the accompanying drawings given by way of example and representing, respectively:

FIG. 1, the functional diagram of an apparatus according to an embodiment of the invention;

FIGS. 2A-2C, a schematic representation of a local annealing stage of a manufacturing process according to the invention;

FIG. 3 a spray nozzle of an adhesion promoter used in a manufacturing process according to an embodiment of the invention;

FIGS. 4A-4E, different conductive patterns made by a manufacturing process according to an embodiment of the invention;

FIGS. 5A-5C, graphs illustrating the evolution of the resistance of different resistive patterns made by a manufacturing process according to an embodiment of the invention as a function of their geometric parameters;

FIGS. 6A and 6B, tensile test pieces equipped with uniaxial strain gauges, made by a manufacturing process according to an embodiment of the invention;

Figures 7a-7C, graphs illustrating the results of measurements made during tensile tests of test pieces of the type illustrated in Figures 6A and 6B;

FIG. 8 a two-dimensional bending sensor produced by a manufacturing process according to an embodiment of the invention;

Figures 9A-9E, the manufacturing sequence of a multiaxial force sensor carried out by a manufacturing process according to an embodiment of the invention and Figure 9F, a side view of this sensor; FIG. 10 is a sectional view of an acoustic sensor produced by a manufacturing method according to an embodiment of the invention;

FIGS. 11A to 11H, flow diagrams illustrating an algorithm for generating a print file for an electrical resistance carried out by a manufacturing method according to an embodiment of the invention;

Figures 12A-12C, illustrations of the notion of filling a surface; Y

FIG. 13, a flow chart illustrating an algorithm for generating a print file for a piezoresistive strain gauge carried out by a manufacturing method according to an embodiment of the invention.

Figure 1 schematically illustrates an apparatus for manufacturing three-dimensional mechatronic objects in accordance with an embodiment of the invention. These objects, made by depositing molten filament and, in particular, of functional thermoplastics, include a mechanical structure, possibly articulated, and electronic components such as passive components (resistance, capacitor, antenna, etc.), sensors and actuators. . The apparatus of Figure 1 allows complex 3D objects to be printed with capabilities for interactions with their environment or the user, with a short design and manufacturing cycle, low costs, great malleability in the shape of the objects and their use .

The apparatus substantially comprises a three-dimensional I3D printer, of the molten filament deposit type - or FDM - adapted for the implementation of a method according to the invention. It may also comprise a printed electrical / electronic component design interface. This interface may comprise a base of BDM data, stored on a computer-readable medium, such as a hard disk, which contains a library of electronic components and transducers made by three-dimensional printing using functional thermoplastics, with their behavior models. It can also comprise a SGF computer system (typically a computer) configured to receive as input, through a user terminal and possibly a graphical interface, the desired electrical and geometric properties of an electrical component and that exploits the models of the database to generate an FI print file containing all the instructions that allow the I3D printer to manufacture the electrical device designed in this way. The steps leading to the generation of the FI file will be described in the continuation of this document, with reference to Figures 11A-11H and 13.

As shown in figure 1, the three-dimensional I3D printer comprises at least two extrusion heads TE1, TE2 arranged side by side, carried by the same printing carriage CI, movable in three orthogonal directions, x, y and z - corresponding to the z direction The direction of extrusion of the two extrusion heads -thanks to an MD displacement mechanism, whose structure is not represented in detail, since it is conventional, controlled by a SIP computer system (computer or microcontroller card). The use of two different extrusion heads facilitates the deposit of at least two different thermoplastic materials: an insulating material M1 used for the manufacture of the mechanical structure SM of the mechatronic system and a functional material (conductive or resistive) M2 used for the manufacture of at least one electrical component CE. The nature of these materials will be discussed in detail later. In general, these will most often be thermoplastic polymer materials or composites having a thermoplastic polymer matrix. At least the material M2 will generally contain charges that influence its electrical properties, for example by making it conductive.

For the realization of complex systems, comprising more than two materials, more than two heads may be used; the same head can be used to deposit several different materials, but this slows down the procedure (some changes of the nozzle feed material have to be carried out) and introduces a risk of contamination.

An ATV drive mechanism allows you to adjust the vertical (z) position of each head relative to the other heads. This makes it possible, in particular, to raise the inactive heads during the realization of complex structures, where the risk of collision between the extrusion heads and the elements already printed becomes important. Even in the case of a single layer by layer printing, residues present on the inactive heads are found to be deposited in an involuntary and uncontrolled way, which can alter the aesthetic properties (color, texture, etc.) and, on all functional of the final object. For example, this can lead to shorts between conductive tracks.

In a conventional way, each extrusion head TE1, TE2 comprises an extrusion nozzle having heating edges and a coil that carries a filament of the thermoplastic material M1, M2 to be deposited to this nozzle. Typically, each die is mounted on a heater block, which transmits heat to the extrusion edges by thermal conduction. The end of the filament in contact with the heating edges of the nozzle melts and the molten material is expelled from the nozzle under the effect of pressure exerted by the not yet melted part of the filament, which acts as a piston.

The control of the quantity of material by the printer can be carried out by a simple weight control, knowing the density of the filament, the weight of the support coil (standard, but it can be deduced from its dimensions and the density of the constituent material ) and the diameter of the filament. Weight can be measured by a simple pressure sensor or a more complex force sensor, which could come from 3D printing itself.

For the sake of accuracy, the real-time measurement of the weight by the sensor can be complemented by a more traditional approach which consists of using a contact sensor to measure the number of rotations made by the coil. At each turn, a counter is incremented by 1. The length consumed for one complete turn is equal to the perimeter of the coil; multiplying this length by the section of the filament and by its density, the amount of matter deposited is obtained.

The reliability of the printing of multimaterial and functional structures depends, in particular, on the precision of the positioning of the different extrusion heads. Reliability is based, first of all, on an automated calibration process for the spacing between the extrusion heads and the PLI build platform (according to the z direction) and for the position of the heads in the (x, y) plane from the platform.

The calibration of the spacing between the extrusion heads and the platform in height (z) and of the flatness of the platform, is generally done thanks to an end-of-travel sensor and an adjustment of the corners of the platform. But when large surface platforms are used (for example, on the order of 20 cm x 20 cm or more), it becomes difficult to ensure their flatness and therefore the use of an end-of-travel sensor is not satisfactory. This is the reason why an apparatus according to the invention comprises a capacitive DC sensor integral with the printing carriage. The use of the capacitive sensor allows to calibrate the platform at various points without touching it and avoid the mechanical inaccuracies inherent in the mechanical end-of-travel sensors commonly used in servo motors. The capacitive sensor acts as a non-contact switch. Unlike an inductive sensor, it detects non-ferrous materials, such as glass, wood, skin, etc. This sensor will, in fact, simply replace the end of travel contact being installed directly on the printing carriage.

Calibration of the position of the extrusion heads in the xy plane of the platform is important, in order to properly align the structural parts manufactured with the different heads.

For a first layer (which makes, for example, a surface of the mechanical structure), an initial calibration is carried out thanks to the capacitive DC sensor with integrated earth electrode and metal earth electrodes (references EET1, EET2 in figure 1) placed in the corners of the platform. Indeed, at a constant distance between the sensor and the platform, the measured capacity will be greater with a metal piece between the two sensor electrodes rather than with the coating or insulating material of the platform.

For the following layers, in particular, when using several print heads and therefore printing several thermoplastic materials, the alignment with the previous layer and with the part printed with another material must be verified with the help of a visual servo control. implementing a CE camera connected to an STI image processing system (which, in the embodiment of figure 1, coincides with the SIP piloting computer system). The visual servo control is carried out as follows:

- an image of the printing surface, on which at least one layer of material has been deposited, is acquired by the camera CE; eventually, multiple images can be acquired and averaged to improve signal-to-noise drift;

- a reference point is chosen on the image, automatically or manually (user intervention); - the position of this reference point on the image taken by the camera is compared with its position on the model of the last layer deposited, already in memory in the printer;

- the position of the printing carriage along the x and y axes is calculated and stored in memory;

- the printing of the top layer takes into account these possible offsets.

Preferably, as in the case of figure 1, the calibration chamber CE is integral with the carriage, with a known position relative to the extrusion heads. As a variant, the camera can be fixed and use a visual coordinate system fixed on the printing carriage to determine the relative position of the latter with respect to the reference point on the image.

A method according to the invention necessarily implements at least two different materials, deposited in superimposed layers. However, the adhesion between heterogeneous layers is not always satisfactory. For this reason, according to the invention, a local annealing is carried out in situ at the same time as, or after, the depositing of a layer. The role of this local annealing is to provide the thermal energy to reinforce the adhesion between two constituent materials of the object; incidentally, it can also make it possible to improve the intrinsic properties of the functional thermoplastic materials used.

Current FDM technology relies on the simple extrusion of polymer layers adjacent to or on top of one another and uses latent heat of extrusion, with or without the aid of a heating pad, to melt and weld adjoining layers. This procedure induces an incomplete or non-uniform welding of the layers and, consequently, reduces the mechanical properties due to a delamination between the layers, in particular, in the case of a load applied perpendicular to the surface of the layer or of the direction filament deposit. This is all the more true for the interfaces between two different materials, where the wetting between the two materials can be partial. During the depositing of the filament of a second on a layer of a first material, the filament of the second material is in the molten state and the wetting of the surface of the layer of the first material depends on the physicochemical parameters of the two materials, such as the surface tensions of the two species, the surface roughness of the first material and the viscosity of the second material. During the manufacture, after the cooling of the part, the delamination of the layers can take place, then, due to the fact of the reduced contact surfaces, the adhesion forces that are too low and the differences between the coefficients of thermal expansion of the two materials.

The annealing carried out during the implementation of the invention is based on the local heating of the materials deposited by means of nano-charges (CM1, CM2 in Figures 2B and 2C), incorporated in the material matrices (MM1, MM2 in these same figures ) and capable of absorbing an electromagnetic beam that radiates at one or more given wavelengths. In the embodiment of figure 1, a source of electromagnetic radiation SRR, for example an infrared laser, is attached to the printing carriage; the reference FL designates the electromagnetic beam generated by the source (in this document, a laser beam, but it could also be another type of radiation, for example, microwaves, see, for example, WO2015130401 or radio frequencies).

Annealing can be carried out during the printing of the layer in question, according to different configurations:

- passage of the beam behind the active extrusion head and an action on the last layer deposited (configuration illustrated in figure 2A; where the reference AT symbolically represents a localized heating);

- passage of the beam independently (extrusion head inactive), with an action on: the last layer or layers deposited in the case of a homogeneous material; the last layer or layers of the first material, located below the second, by transmission through the latter, which is transparent at the wavelength used.

The annealing system has been represented very schematically in Figures 1 and 2A; in practice, it will comprise a radiation-emitting source, a focusing system (possibly integrated in the source) and a beam guiding system to the point of impact, typically an optical fiber. In the embodiment of FIG. 2A, the annealing radiation source SRR is integral with the printing carriage, but in other embodiments it may be independent.

The radiation-absorbing nano-fillers can be selected from the group consisting of carbon nanotubes, carbon black, buckyballs, graphene, supermagnetic nanoparticles, magnetic nanoparticles, metallic nanowires, semiconductor nanowires, quantum dots, polyaniline (PANI), poly3,4- ethylenedioxythiophene polystyrenesulfonate and its combinations. Their choice will be made not only on the basis of its functionality thus transferred to the compound (for example, an electrical conductivity), but also on the basis of the wavelength of the radiation corresponding to the maximum optical absorbance of the charge and , therefore, an optimal heating for a minimum power. For example, a number of fillers have high microwave absorbance, for example metals, oxides, carbon (specifically, "CNT" carbon nanotubes), and conductive polymers (eg, polypyrrole). The use of radio frequency radiation (of the order of ten MHz) is, for its part, adapted for ceramic charges, such as SiC, ZnO or TiO2. The use of an infrared laser is particularly effective for uncharged or charged matrices of fibers (eg, carbon fibers). Radiation absorbing fillers may already be present in the molten filament or may be deposited by spraying from a suspension.

Annealing allows the interdiffusion of the polymer chains of the matrices between the adjacent layers (figure 2C), limiting at the same time the heating of the rest of the part and thus significantly reducing the alteration of its dimensions, in particular, by creep and change of thermal cycle.

The distribution and distribution of the CM2 functionalization charges in the deposited filaments may change during the extrusion process or may not be optimal initially. Local annealing in situ also makes it possible to homogenize the distribution of charges in the matrix volume, to reform a maximum of percolation networks (conductor, semiconductor or dielectric depending on the nature of the charges) and, therefore, to improve the functional properties of the compound in the final structure. This is schematically illustrated in Figure 2B.

The deposit of an adhesion promoter at the interface between two parts made up of different thermoplastics and, specifically, with different matrices in the case of composites, can be used as a replacement or complement to irradiation beam annealing and improve adhesion between these two parts. This deposition is made thanks to a droplet spray nozzle, for example, a valve with air for atomization, air for control and liquid adhesion promoter. A device of this type is represented very schematically in figure 3, where it is identified by the reference BP; the reference APA designates the jet of adhesion promoting agent.

The spray deposition profile of the adhesion promoter on the surface is known to be Gaussian and centered on the point in front of the spray. In order to obtain a concentration profile as uniform as possible, it is therefore convenient to program passage paths for the spray nozzle. The adhesion promoter can be a homogeneous liquid or a suspension of nano or micrometer particles. In the latter case, it will be necessary to make sure to have a homogeneous suspension beforehand during its preparation, in particular, thanks to some stages of sonication, then centrifugation. In all cases, the reaction of the adhesion promoter with the interfaces and / or the vaporization of the solvent should ultimately leave a solid adhesion layer. Moreover, it is envisaged that the spraying device can allow the deposit of absorbent particles, which once taken as a sandwich between two layers, of the same thermoplastic or of two different thermoplastics, can be irradiated with the beam described above and allow to improve adhesion. thus.

As mentioned above, the structure material M1 of a mechatronic object according to the invention is an electrical insulating material. The framework material may be a polymer, such as a thermoplastic, a thermoplastic elastomer, a ceramic or a ceramic or thermoplastic matrix composite. The thermoplastic matrix may be part of the group, but not only, that consists of acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamide (Nylon), polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyurethane (PU), polycarbonate (PC), polyphenylsilphone (PPSU), polyether ether ketone (PEEK) and their mixtures. The ceramic may be selected from the group consisting of oxides, carbides, borides, nitrides and silicides. For example, compatible ceramics consist of silicon nitride, PZT, aluminum oxide or also hydroxyapatite. The compounds used can incorporate any type of fillers, which allow their mechanical and thermal properties to be modified and adjusted, such as ceramic or metallic fillers, glass or carbon fibers or carbon particles.

The electrical component (s) are made of at least one functional thermoplastic material M2, which is generally a compound that has properties such as good electrical conductivity and / or piezoresistivity or piezoelectricity and / or good thermal conductivity and / or a high dielectric coefficient, etc. For example, for an electrically conductive thermoplastic, the charges can be part of the group of carbon particles, which consist of carbon black, graphene, carbon nanotubes. To obtain good thermal conductivity, metal fillers or nanotubes can be incorporated. This material must have the properties suitable for shaping by FDM, namely a melting temperature close to that of the structural material (s) and less than 300 ° C and a sufficiently low viscosity in the melting zone. For this, one solution is, as far as possible, to use a polymer matrix identical or similar to that of the M1 structure material. Used alone or associated with another thermoplastic, functional or not, functional thermoplastic M2 enters into the manufacture of an electrical or electronic component, such as a passive component (resistor, capacitor, antenna, etc.), a sensor or an actuator.

In order to take full advantage of the advantageous characteristics of an apparatus and of a method according to the invention, it is possible to develop and integrate new thermoplastic materials having functional properties that make it possible to produce electronic components, sensors and actuators.

The integration of these materials requires exhaustive electrical and mechanical characterizations, in order to identify the parameters to be adjusted to guarantee optimal functionality in the 3D mechatronic object. To this end, the inventors have been interested, in particular, in the following composite thermoplastics:

- material 1: ABS matrix / CB loads (carbon black)

- material 2: PLA matrix / CB loads

- material 3: PI-ETPU matrix (polyimide / engineering thermoplastic polyurethane) / CB fillers

- material 4: PLA matrix / CNT charges (carbon nanotubes)

- material 5: PLA matrix / graphene fillers

The materials that have been the object of these characterization studies are thermoplastics loaded with carbon particles that have a high intrinsic electrical conductivity. These compounds have an electrical conductivity that depends not only on the nature of the charges, but also on their concentration and distribution in the thermoplastic matrix. The concentration of the fillers must be sufficient to allow the formation of a conduction path or percolation, but low enough so that the viscosity of the filament allows the continuous extrusion of the molten filament in a temperature range below 300 ° C. The distribution of charges in the composite filament depends on the process of shaping the composite filament (single or double screw extrusion), the control of the process parameters and the preparation of the particles with potential surface functionalization. A homogeneous distribution and distribution of the charges allows a greater number of percolation paths and, therefore, a better electrical conductivity of the compound. But ultimately, the electrical properties of the composite are also modulated by the procedural and geometric parameters used during FDM 3D printing of the object.

As indicated above, the viscosity, malleability and hardness of the five compounds studied are not the same due to the fact that their matrices, their charges and their conformation differ. For this, the parameters of the procedures must be adapted, in order to allow a continuous extrusion of the filament. For the studied materials, the extrusion temperature depends mainly on the thermoplastic matrix used: 210-220 ° C for loaded PLA, 230 ° C for loaded ABS and 220 ° C for loaded PI-ETPU. However, it is clear that these values have been optimized by the manufacturers and, in particular, by adopting the appropriate concentration of loads.

The speed of movement of the nozzles during printing or printing speed, is governed, however, by other parameters than viscosity.

The extrusion of the filament is allowed thanks to the gear of the filament, pinched between a fixed wheel and a moving wheel and the upper part of the filament, solid, makes a piston on the lower part, liquid. The malleable filaments have a tendency to buckle under the effect of compression stress and this despite a design of the extrusion head that allows limiting the lateral movements of the filament. Lowering the speed, typically 20 mm / s, allows time for the molten filament to extrude and remain below the yield stress for malleable filaments.

Carbon nanoparticles, for example CNTs and graphene, are not only good electrical conductors, but also good thermal conductors. Too low a print speed runs the risk of allowing the core of the molten filament to cool by internal thermal conduction, despite contact on the edges with the hot nozzles. This phenomenon needs to limit the transit time of the filament at the nozzle, so that it is long enough to allow liquefaction of the filament and short enough to prevent resolidification of the core. In this case, a high printing speed, typically 80 mm / s, allows to have a continuous extrusion and avoid the clogging (clogging, in English) of the nozzle.

A last parameter must be taken into account depending on the nature of the thermoplastic matrix and its behavior in the molten state, it is the distance between the nozzle and the platform for the first layer. Indeed, a high viscosity and elasticity require a greater spacing, as for ABS with respect to PLA in the first case and for PI-ETPU with respect to PLA in the second case.

In order to carry out mathematical models of the electrical components that can be manufactured in accordance with the invention, rectangular bar-shaped patterns have been made and characterized from the five materials above. These patterns differ by their length L (fig. 4A), width W (fig. 4B), overall thickness H (fig. 4C), thickness e of each elemental layer or "stratum" (fig. 4D) and printing direction (fig. . 4E). An electrical characterization This exhaustive analysis has made it possible to classify materials based on their conductivity and establish laws that connect the resistance of the patterns with the geometric parameters mentioned above.

Figure 5A shows the evolution of the resistance of a rectangular bar (W = 20 mm, H = 400 | jm, printing direction with respect to the length of the bar = 0 °, T = 200 jm) as a function of its length L for the 5 materials studied. The most conductive materials are easily identifiable: conductivity decreases when the index of the material increases from 1 to 5. Figure 5B shows the evolution of the average relative resistance of the bars (L = 50 mm, H = 0.4 mm, direction impression with respect to the length of the bar = 0 °, T = 20o jm) as a function of its width for the 5 materials studied. The average relative resistance is given by (R-R0) / R0, where R is the resistance of the considered bar and R0 that of a reference bar that has a length equal to 10 mm. Reverse law evolution is valid for everyone, which demonstrates their ohmic behavior. Figure 5C shows the evolution of the average relative strength of the bars as a function of their width (L = 50 mm, H = 0.4 mm, printing direction with respect to the length of the bar = 0 °, T = 200 jm) and its height (L = 50 mm, W = 20 mm, printing direction with respect to the length of the bar = 0 °, T = 200 jm) for Material 4. The resistance is inversely proportional to the width and at the height of the bar, with the unit power.

The relative variation of resistance R of the standards as a function of length L, width W and height H, is almost identical for the five compounds. Qualitatively, in Figures 5A-C, it is also noted that the charged thermoplastics once printed behave like ohmic conductors and that the resistance obeys the general expression:

where p is the resistivity of the bar measured over its length. This ohmic behavior is, on the other hand, supported by a number of current-voltage characteristics performed on the different manufactured samples.

The resistance also varies as a function of the printing direction and according to the law above, it is possible to empirically connect this variation with the intrinsic resistivity of the printed pattern, that is, with its microstructure. The results obtained are reproduced in table 1 below. The resistivity of the bar increases when the printing direction goes from 0 ° to 45 °, then 90 °. This angle is evaluated with respect to the length of the bar.

Table 1 - Resistivity of conductive thermoplastics and printing directions.

On the other hand, the influence of the thickness "e" of the printed layers on the resistance is negligible for most of the materials, except for Material 3. The decrease in resistance by a factor of 2.5 when e varies between 100 and 300 jm for Material 3 could be explained by a vertical continuity between the layers (less homogeneous layer-layer interfaces) that potentially allows a greater number of percolation paths. In this case, the use of a local anneal, as described in the present invention, would allow to form new percolation paths at the interlayer interfaces and would significantly improve the electrical conductivity of the printed pattern.

In order to characterize the piezoresistivity thereof, Materials 1 to 5 have been used to manufacture FDM-printed uniaxial dumbbell tensile test pieces.

These test pieces have been designed by exploiting the difference in resistivity as a function of the printing direction and with dimensions in accordance with the ASTM D638 standard, that is, for the useful part: L = 50 mm, W = 10 mm, H 300 jm. For each material, copies have been printed entirely in printing directions, measured with respect to the length of the test piece, of 0 °, 45 ° or 90 °. A few examples ET1 (0 °), ET2 (90 °) of the manufactured test pieces are illustrated in Figures 6A and 6B.

The traction has been exerted by means of vertically suspended weights in the lower part of the sample, while the upper part of the sample was fixed by a clamp to the frame. The suspended masses were 100 g, 200 g, 500 g and 1 kg. Assuming that the test pieces have no defects, the stress was concentrated on the useful part and the applied stress varied between 3 and 33 MPa.

The results of the tests are illustrated in Figures 7A-7C.

Figure 7A illustrates the evolution of the electrical resistance R of the Material 2 tensile test pieces as a function of the mass M of the vertically suspended weight. The fill rate is 100%, the test piece is therefore solid.

Figure 7B illustrates the evolution of the electrical resistance of the tensile test pieces, under zero loading or 100 g, during a change in the mechanical loading / unloading cycle. The test pieces considered in this document have a fill rate of 80%, which means that there is a spacing between the filaments or stripes, which form the body of the test piece, of which approximately 20% is made up of empty spaces.

Figure 7B illustrates the evolution in time t of the electrical resistance of the tensile test pieces following the removal of a 100 g load. Following a sharp increase, the resistance progressively decreases towards the rest value.

Among the materials studied, Material 3 has demonstrated piezoresistive behavior with a threshold effect, when the test piece is printed at 90 °, as translated in Figure 7A. The threshold from which the resistance variation appears can be lowered by decreasing the fill rate during FDM printing, that is, by modulating the quality of the contact between the stripes. If the fill rate is high, there will be overlap between adjacent stripes. The more this rate decreases, the thickness of the extrudate being constant, the more the part where there is overlap decreases and the interface between the adjacent stripes sees holes or porosities appear, where the air is trapped. Therefore, the porosity rate is an important parameter that allows to control the resistance and piezoresistivity threshold of the printed pattern. After a purification cycle (breaking of the scarce paths that occurs during the first uses, which leads to rapid variations in electrical properties followed by a stabilization phase), it is noted that the resistance variation appears from 100 g of loading for a bar with a fill rate of 80%, with good repeatability and endurance of at least 10 cycles (see Figure 7B).

The same piezoresistive behavior is observed for the test pieces whose stripes are printed at a printing angle of 90 ° with respect to the length of the test piece with Material 5. However, a matrix relaxation phenomenon is observed of elastomer following loading or unloading. For discharging, this phenomenon induces a sudden increase in resistance, then a logarithmic decrease towards the rest value (see Figure 7C). This temporal response is, thus, a not insignificant problem in the reliability of the measurement and its exploitation to make a sensor.

The behavior models and laws established for the piezoresistivity of Material 2 and those established for the resistivity of conductive thermoplastics allow making sensors that take advantage of these properties.

Figure 8 represents a functional CF2D two-dimensional flexure sensor, entirely printed by FDM with 3 different thermoplastic materials. Indeed, this component comprises a SM structure of insulating thermoplastic (ABS), 4 contact electrodes ELC1, ELC2, ELC3, ELC4 of conductive thermoplastic (Material 4) and 2 central parts JC1, JC2 of charged thermoplastic that has piezoresistive behavior ( Material 2), printed according to orthogonal printing directions, which form strain gauges, supported by the mechanical structure SM and whose sensitivity axes (determined by the printing direction and, therefore, by the alignment of the constituent filaments) they are mutually perpendicular.

In order to avoid the downtime required for coil changes, the sensor has been printed using three extrusion heads, one per material. A thin layer of adhesion promoter has been deposited on the heterogeneous interfaces.

The central parts of the sensor are, respectively, a rectangle JC1 of Material 2 printed at 0 ° and a rectangle JC2 of Material 2 printed at 90 °, with a thickness of 600 pm. According to the characterization results, only the rectangle whose printing direction is perpendicular to the tensile stress direction produces a change in electrical resistance. The other block retains the same resistance. The juxtaposition of these two blocks therefore makes it possible to measure a stress along the x-axis or the y-axis, even a biaxial stress in tension.

When the ABS substrate experiences a bending stress, its upper face is stressed in tension. This requirement is transmitted to the Material 2 blocks by shear at the interface. The results obtained with this sensor and that demonstrate its functionality, are presented in table 2 below:

Table 2.

The freedom of form allowed by the procedure and the availability of conductive and piezoresistive thermoplastics, allows the realization of multidimensional force sensors. Figure 9F shows a side view of a sensor of this type that is in the shape of a mini-control lever that can transduce the force applied to the central connector and its x and y components. This sensor has an insulating mechanical structure that comprises an annular substrate Sa, some support pillars PS and a central platform PTC made of insulating material; piezoresistive elements PZR1-PZR4 forming suspended bridges made with the aid of a printed support made of sacrificial polymer, for example soluble; some contact electrodes EC1 - EC5, the central control lever JC and some conductive pillars PC1 - PC4 for hooking the connection system. Figures 9A-9F show these different elements separately.

Figure 10 illustrates an acoustic sensor of the piezoresistive type, also produced by a printing method according to the invention. It comprises an insulating mechanical structure SM, two contact electrodes ELC1, ELC2 made of conductive thermoplastic, two conductive membranes MC1, MC2, likewise, made of conductive thermoplastic, which form the two frames of a capacitor and some strain gauges JC1, JC2, each connected to a respective contact electrode and to the conductive membrane MC1. Strain gauges make it possible to measure the deformations of the MC1 membrane under the effect of an acoustic wave.

As referred to hereinabove, a layout interface is advantageously provided to facilitate the layout of the printed electrical components. This interface is a computer system (computer, computer network, microprocessor card ...) programmed to receive as input some parameters of an electrical component to be manufactured, such as the desired electrical properties, the position of its contact points. , its location within or on the surface of a mechanical structure ... and provide the output, thanks to the application of appropriate algorithms, a print file (typically in the GCode format) that allows the piloting of the three-dimensional printer.

The flow diagrams of Figures 11A to 11H illustrate, by way of non-limiting example, the algorithms that allow the print file to be produced for a simple electrical component, namely, a resistor deposited on an insulating substrate. Figure 13 also illustrates, by way of non-limiting example, an algorithm that makes it possible to generate the print file for an axial strain gauge.

A resistor manufactured by three-dimensional printing can be two-dimensional (that is, planar, deposited on a surface) or three-dimensional - passing, therefore, through non-coplanar points, which can be imposed. In the case of a two-dimensional resistance, a linear geometry can be adopted - for low resistance values - or zigzag or serpentine - for higher resistance values. These three different cases require different design algorithms. In this way, as illustrated in figure 11A, the user of a design interface according to the invention first defines the thermoplastic material to be used (step EA1), whose properties are known and stored in the database of BDM models and the resistance value R_user (R_user) to be reached (stage EA2), then (EA3) indicates whether the resistance is three-dimensional or must respect some imposed passage points. If so, the design interface will apply a three-dimensional resistor design algorithm, illustrated in Figures 11G and 11H. Otherwise, the system will determine autonomously (EA4), based on the value R_user (R_user), if it is convenient to perform a linear geometry (for example, if R_user (R_user) is less than a predefined threshold R_th), in which In this case, it will apply the algorithm illustrated in Figure 11B or a zigzag geometry (for example, if R_user (R_user) is greater than or equal to R_th), in which case it will apply the algorithm illustrated in Figures 11C to 11F. The choice between a linear and zigzag geometry can also take into account other parameters, for example, the space required or be left to the discretion of the user.

Whatever the chosen geometry, the applied design algorithm defines the volume of the resistance to be manufactured (EA5). Next, (step EA6) a CAO (Computer Aided Design) modeler generates a triangular lattice of this triangle-shaped volume, which is typically recorded in the form of a stereolithography file in the STL format. Next, we proceed (step EA7) to cut into sections ("slicing" in English) of the volume defined by the STL file, which allows defining each section of material deposited by the extrusion head and associating a displacement path there print head. The trimming is carried out by a software of a type known per se, which depends on the printer, which preferably also allows the latter to be parameterized by determining, in particular, the temperature of the edges of the nozzle, the rate or the filling angle. , etc.

All the nozzle movements and the machine parameters are recorded in the FI print file, for example in the GCode format.

The flow chart in Figure 11B illustrates the design algorithm for a linear resistor.

To begin, the user provides as input to the computer system the width Xmax (EB1) and the length Ymax (EB2) of the region, which is supposed to be rectangular, which contains the resistance, the position of the point that serves as the origin of the system of coordinates defined in this region (EB3), as well as the coordinates of the contact points A and B of the resistance in this coordinate system (EB4, EB5); these points are generally located on some sides of this rectangular region, in any case, this will always be the case in the continuation. The computer system then calculates the length L of segment AB (EB6), then the section S = p L / R_user (R_user) necessary to obtain the desired resistance (EB7), where p is the resistivity of the material, extracted of the BDM base.

The section S is the product of the width W of the resistance and its thickness H, these two quantities being to be determined. The thickness H of the resistance is an integer multiple of the thickness e of a section of material deposited by the extrusion head, while the width W is between a minimum value Wmin as a function of the extrusion head and the admissible width of the resistance, Wmax. We start by assuming H = e and calculate the corresponding width: W = S / H. If a value greater than the maximum allowable width Wmax is found, H is increased by the value e and thus subsequently. Although this is not illustrated in the figure, it is possible that even with H = e we will obtain W <Wmax. This means that R_user (R_user) is too high; Therefore, it is necessary either to increase the length L by moving one of the contact points (or both), or to change the material, or to use a zigzag geometry. In principle, this situation should not arise if the linear geometry has been selected automatically by the algorithm of Figure 11A. These operations constitute stage EB8.

Next, (EB9) it is verified that the value R = RHOL / S is well equal to R_user (R_user). If this is not the case, the user has the possibility to change the used material, in which case the algorithm resumes from step EB7; If you don't want to, the computer system shifts one of points A and B (or both) to change the length L until R = R_user (R_user) (EB10).

The algorithm for designing a zigzag resistor is illustrated in Figures 11C through 11F.

As in the case of linear resistance, the user provides as input to the computer system the width Wmax (EC1) and the length Ymax (EC2) of the region, which is supposed to be rectangular, containing the resistance, as well as the coordinates the origin of the coordinate system (EC3). Likewise, it provides the width W and the thickness H of the resistive "wire" that forms the zigzag pattern (EC4, EC5), which allows the system to calculate the length of this wire: L = R_user (R_user) WH / RHO ( EC6). Next, the user provides as input the coordinates of the contact points A and B of the resistor (EC7, EC8), which allows the system to determine if these points are on opposite sides of the rectangular region, on a same side or on adjacent (and orthogonal) sides. To these three figure cases correspond three different algorithms, which are illustrated by Figures 11D, 11E and 11F, respectively.

When point B is in front of A (figure 11D), the path of the conductive wire is determined starting from point A (step ED1), moving in a predefined step of length DELTA_min (small with respect to the dimensions of the rectangular region containing the resistance, but greater than the width W of the wire) towards the side where B is located and perpendicular to the side where A is located (ED2). Then, it travels parallel to the side of A, in the direction of the vertex on this side farthest from A, stopping at a DELTA_min distance from the edge of the rectangular region, to preserve a margin of safety (ED3). Then, it also moves one time of the length DELTA_min towards the side where B is located and perpendicular to the side where A is located (DI4). The distance traveled since the beginning is then memorized and stored in a variable dist_p (DI5). At this point, the minimum distance that remains to be traveled, in a straight line, to reach B (ED6) is calculated. If the sum of dist_p and this minimum distance exceeds L (calculated in step EC6), this means that it is not possible to perform a zigzag resistance of the desired value; therefore, you have to change the material. Otherwise, the system determines whether points A and B are opposite in the x direction or in the y direction. In the continuation, only the first case is considered (steps ED7, ED8, ED9); the operations carried out in the opposite case are completely similar (steps ED7 ', ED8', ED9 ').

The zigzag resistance is substantially constituted by a certain number nb_p of patterns (meanders) formed by a short line, of length d, in the direction perpendicular to the sides that lead A and B (direction x, in the example considered in the present document) and by a long stroke, of length D, in the perpendicular direction, plus two end segments - of a length dist_p on the side of A and of a length to be calculated on the side of B. During step ED7 , it seeks to solve the system:

nb_p- (d + D) <L-dist_p

nb_pd <Xmax-2DELTA_min

making a hypothesis about the value of D (since there are three unknowns and only two inequalities). The initial hypothesis is: D = Ymax-2DELTA_min.

During step ED8, it is verified if the solution found verifies the condition d> DELTA_min. If this is not the case, the value of D is decremented from DELTA_min (DI9) and step DI7 is executed again.

The final piece is constituted by the shortest path that connects the terminal end of the last pattern with B (ED10). In general, to obtain a total length equal to L, it will be necessary to adjust the length of the last long stroke (penultimate piece of the resistor, which, therefore, will not necessarily be equal to D. To build the volume of the resistor from of the path determined in this way, then, there remains only to apply the width of the wire W (ED11).

When point B is on the same side as A (figure 11E), the path of the conductive wire is determined starting from point A (step EE1), moving in a predefined step of length DELTA_min (small with respect to the dimensions of the rectangular region containing the resistance, but greater than the width W of the wire) in the direction perpendicular to the side where points A and B meet (EE2). Then, (EE3) moves parallel to this side and in opposition to B, until leaving no more than a safety distance DELTA_min on the side perpendicular to the starting side. Then, it also moves the distance DELTA_min in the direction of the first offset, that is, perpendicular to the side that leads A and B (EE4). The next steps - EE7, EE8 to EE10, EE8 'to EE10', EE11, EE12 - are identical to steps ED6, ED7 to ED9 and ED7 'to ED9', ED10 and ED11 described above.

When point B is on an adjacent side and, therefore, perpendicular, to which point A leads (figure 11F), the path of the conductive wire is determined starting from point A (step EF1), moving in a predefined step of length DELTA_min (small with respect to the dimensions of the rectangular region containing the resistance, but greater than the width W of the wire) in the direction perpendicular to the side where point A (EF2) is located, then, moving parallel to this side and in the direction of the opposite side to that bearing point B, up to a safety distance DELTA_min from the latter (EF3). Next, it moves parallel to this side until leaving a safety distance DELTA_min on the opposite side to that of A (EF4). The continuation (steps EF5 -EF11) is identical to the previous cases.

The last figure case, that of a three-dimensional resistance, is the subject of Figures 11G and 11H. First, the user must define a volume in which the resistance, the starting points (A) and the arrival points (B), as well as some intermediate points of passage (EG1) are defined. It is important to note that, in the FDM three-dimensional printing technique, a volume is presented in the form of a stack of layers of predefined thickness. Therefore, the position of a point can be defined by identifying the layer to which it belongs and giving its two-dimensional coordinates inside the latter. To define the resistance path, we start from point A (EG2), identify the projection pt_s of the next point of passage on the layer containing A - or, more generally, the current point pt_c (EG3) and determine the distance to travel to reach this projection (EG4), as well as the difference in height between the layer of the current point and that of the next point (EG5). The distance L_cs between the points pt_c and pt_s is the sum of the distance in the plane, determined in step EG3, and the difference in height (EG6); this distance is memorized. Then, it goes to the next point and, thus, until reaching point B. Then, L_calc is calculated, the sum of the lengths L_cs (EG7). The knowledge of the resistivity RHO of the material allows, then, to calculate the section S of the resistive pattern (EG8); From the knowledge of this section, the thickness and width are calculated as explained with reference to the linear case of Fig. 11B (step EG9). Then, it is verified if the resistance obtained in this way, R_calc, has the value that we want R_user (R_user) (EG10). If R_calc, <R_user (R_user) and if the user does not want to change the material, it is necessary to replace at least some of the straight segments that connect two successive passage points within the same layer with zigzags. To do this, the length of each intermediate segment is expressed as a percentage of L_calc (EG11) and a resistance to be reached is attributed to it that corresponds to the same percentage of R_user (R_user) (EG 12). Then, proceed as in the case of figure 11D - stages EG13 - EG16 correspond to stages ED2 - ED5, stages EG17, EG18, EG19 to stages ED7 to ED9 and ED7 'to ED9' and stages ED20, ED21 to steps ED10 and ED11.

Another example of an electrical component that can be manufactured by three-dimensional printing in accordance with the invention and whose manufacture can be facilitated by the use of a programming interface, is a uniaxial strain (or stress) gauge of the piezoresistive type.

The relative variation of resistance AR of a piezoresistive element that presents a resistance at rest R0 is equal to:

AR / R0 = k-e

where k is the piezoresistive sensitivity and e the deformation, with e = AL / lo, where AL is the length variation and L is the length at rest of the element. During sensor design, the initial length (and therefore resistance) is a function of the fill rate of the sensor volume.

Like any element manufactured by FDM three-dimensional printing, a piezoresistive sensor is made up of filaments or bands; this structure is illustrated in Figure 12A. The sensor works by moving the bands closer or farther under the effect of a stress. Indeed, if the bands are brought closer together, microcontacts are created which cause the resistance to drop. Conversely, if the bands move apart, the current flowing is lower. It is understood that sensitivity to deformations is much more important for deformations parallel to the small fill axis, indicated by d in Figure 12A, than for deformations parallel to the large axis D.

If the fill rate is equal to 100%, which means that the belts are perfectly joined and in contact with each other over their entire length, the resistance variations will not be measurable. The same will happen in the case of too low a fill rate. Empirically, it has been found that filling rates of 40 to 70% give completely acceptable results for most of the materials considered.

A comparison of Figures 12A and 12B shows that a filling at 40% (Figure 12A) implies a shorter filament length than with a filling at 70% (Figure 12b). In a sensor with a fill rate of the order of 70%, the conductivity depends significantly on the percolation of the current, that is, on the presence of conductive micropaths that connect the meanders to each other. These micropaths can be easily interrupted by few deformations of the structure, which means that a sensor that has a high filling rate - but not too much, for example, of the order of 70% - will be able to detect smaller deformations. than a sensor with a fill rate of only 40%. However, such a sensor will also be more sensitive to manufacturing defects, for example short circuits caused by a dirty extrusion head. It should be noted that, in the examples of Figures 12A and 12B, several layers of resistive material have been deposited, with perpendicular deposition angles, which leads to isotropic piezoresistive sensitivity.

The flow chart of Figure 13 illustrates the design steps of a piezoresistive stress sensor. First, (EP1 step)

The user makes the desired shape in the CAO software and imports it in STL format (grid with some triangles of the volume). Then, in order to be sure that the sensor will be flexible and strong enough, its height H is set to a predefined value, for example three times the printing thickness e (EP2).

The last layer will serve as a sensor. The other layers can, for example, be made of insulating material with a fixed filling, generally between 60 and 100% and, for example, equal to 70%, to leave more or less flexibility to the sensor (EP3). As a variant, conductive or resistive layers that have another function can also be present below the one that serves as a stress sensor.

On the sensor layer, the user defines the position of the electrodes (EP4) and chooses the resistive material, from a list that is proposed (EP5), as well as the sensitivity that is wanted - also, from a list of possible values (EP6). Filling is generally done in a rectilinear mode (EP7), with a main filling direction perpendicular to the axis defined by the two electrodes (EP8).

A table, built during a previous calibration stage and recorded in a memory of the computer that executes the procedure, allows finding the filling rate that allows reaching the desired sensitivity, given the chosen material and the desired geometry (EP9) .

The printing speed (EP10) can be determined as a function of the fill rate, also determined, typically by means of another correspondence table constructed by calibration. For example, a low print speed can be chosen for high fill rates to avoid short circuits that can occur when filament residue sticks to the nozzle and suddenly peels off during printing. For lower fill rates, the spacing of the passage lines, and therefore the absence of matter in the nozzle passage, is generally sufficient to prevent residue from sticking; therefore, it can be printed at a higher speed, for example 60mm / s. As a variant, a relatively low print speed (eg 30mm / s) can be used regardless of the fill rate.

The invention has been described with reference to mechatronic systems that include piezoresistive sensors. However, the invention is not limited to this figure case. Indeed, it is possible, in particular, by choosing the fillers contained in the thermoplastic matrix in a timely manner, to print by FLM materials sensitive to temperature, light, chemical agents, etc. to obtain thermal, optical, chemical sensors, respectively. On the other hand, from conductive and insulating materials, it is possible to manufacture capacitive or inductive sensors and antennas usable in transmission and / or reception. It is also possible to create thermal, electrostatic, magnetic actuators (using ferromagnetic charges) or even piezoelectric ones. It is also possible to print OLEDs (organic light-emitting diodes) and / or organic photovoltaic cells.

In certain cases, the invention will allow the realization of a fully printed mechatronic system. In other cases, only a part of the electrical / electronic sub-assembly of such a system (sensors, conductive lines, actuators ...) will be printed, while other components - for example, integrated circuits that perform complex electronic functions, may be incorporated. Even in the latter case, the invention makes it possible to reduce the number of assembly operations and, therefore, to make the manufacture of the mechatronic system faster and less expensive.

References

[Coiai, 2015] Serena Coiai et. Al, "Nanocomposites Based on Thermoplastic Polymers and Functional Nanofiller for Sensor Applications", Materials, vol. 8, pages 3377-3427, 2015.

[Deng, 2014] Hua Deng et al., "Progress on the morphological control of conductive network in conductive polymer composites and the use as electroactive multifunctional materials", Progress in Polymer Science, vol. 39, pages 627-655, 2014.

[Muth, 2014] Joseph T. Muth et al., "Embedded 3D Printing of Strain Sensors within Highly Stretchable Elastomers", Advanced Materials, vol. 26, pages 6307-6312, 2014.

[Sitthi-Amorn, 2015] Pitchaya Sitthi-Amorn et al. "MultiFab: A Machine Vision Assisted Platform for Multi-material 3D Printing" ACM Transactions on Graphics (SIGGRAPH 2015).

[Rossiter, 2009] Jonathan Rossiter et al. "Printing 3D dielectric elastomer actuators for soft robotics" Proc. of SPIE Vol. 7287, 72870H (2009).

[Leigh, 2012] Simon J. Leigh et al. "A Simple, Low-Cost Conductive Composite Material for 3D Printing of Electronic Sensors", PLOS ONE, Vol. 7, Issuer 11, e49365 (Nov. 2012).

[O'Brien, 2015] Jonathan O'Brien et al. "Miniaturization of Microwave Components and Antennas Using 3D Manufacturing" 9 a European Conférence on Antennas and Propagation (EuCAP), Lisbon, 13-17 May 2015.

Claims (10)

1. Manufacturing procedure of a mechatronic system that includes: - a stage of manufacturing a mechanical structure (SM) by three-dimensional printing by depositing molten wire of at least one first electrically insulating material (M1) (M1); Y - a manufacturing step of at least one electrical component (CE) in contact with at least one element of said mechanical structure and integral with it; said manufacturing step of at least one electrical component is implemented by three-dimensional printing by depositing molten wire of at least one second material (M2), conductive or resistive, directly in contact with said element of the mechanical structure, characterized in that said or a said electrical component is a transducer (JC1, JC2), The process also includes a local annealing stage implemented during or after the deposit of a layer of the first or second material, corresponding to said deposit. 2. Method according to claim 1, wherein said transducer (JC1, JC2) is a piezoresistive sensor. 3. Process according to one of the preceding claims, wherein said second material, conductive or resistive, comprises conductive charges (CM2) dispersed in a thermoplastic insulating matrix (MM2). 4. Process according to one of the preceding claims, also including a step of depositing an adhesion promoting agent (APA) on a surface of the mechatronic system during manufacture before depositing, above said surface, of a layer of a different material. Method according to one of the preceding claims, comprising the use of at least two different extrusion heads (TE1, TE2) for depositing the first and second material. Method according to one of the preceding claims, also comprising a step of generating a print file (FI) for the production of at least one said electrical component, said step being implemented by computer and comprising: - a substep consisting of providing said computer with data indicative of a position of one or more contact points, of a spatial region where said component must be manufactured and of at least one electrical property of said component; - a sub-step of calculating a geometry of said component by applying said data from a predefined mathematical model; Y - a sub-stage of generation of said printing file that allows to make said geometry by three-dimensional printing by depositing molten wire of said or at least one said second material, conductive or resistive. 7. Apparatus for implementing a method according to one of claims 1 to 6, comprising a three-dimensional printer (I3D) of the type by depositing molten yarn that has at least two different extrusion heads (TE1, TE2), which can be activated from independently and adapted to deposit two different materials, said extrusion heads being arranged side by side with the same extrusion direction and being carried by the same printing carriage (CI) that ensures their simultaneous movement, including the print head likewise, a mechanism (ATV) to move an inactive extrusion head in a direction opposite to said extrusion direction when said or another said extrusion head is active, characterized in that said printing carriage is equipped with a capacitive sensor (CC) configured to measure its distance from a printing surface and because the apparatus also comprises a generator (SRR) of a beam of electromagnetic radiation, said generator being configured to produce local heating of a material deposited on a printing surface of said three-dimensional printer. Apparatus according to claim 7, also comprising a printing platform (PLI) above which said printing carriage moves, said platform being equipped with metal electrodes (EET1, EET2) capable of being detected by said capacitive sensor, by means of which said sensor allows a calibration of the position of the printing carriage with respect to the platform. Apparatus according to one of claims 7 to 8, equipped with: - a camera (CE) configured to acquire an image of a layer of material deposited by the three-dimensional printer; - an image processing system (ITS) configured to compare said image with a three-dimensional model stored in a computer memory and deduce therefrom a position error of said printing carriage; Y - A computerized steering system (SIP) of said carriage configured to correct said position error during the deposit of a successive layer of material. Apparatus according to one of claims 7 to 9, also comprising a computer system (SGF) of generation of a print file (FI) to control said three-dimensional printer to manufacture an electrical component, said computer system being configured to: - receiving as input data indicative of a position of one or more contact points, of a spatial region where said component must be manufactured and of at least one electrical property of said component; - calculating a geometry of said component by application to said data of a predefined mathematical model; Y - generating a printing file that allows to make said geometry by three-dimensional printing by depositing molten wire of at least one conductive or resistive material.